This invention relates to a charge forming device and control therefore for a multi cylinder, two stroke internal combustion engine and more particularly to an improved fuel injection device and control therefore.
It has been recognized that there is a need for providing more accurate control of the amount of fuel supplied to an engine. Obviously, operating with the optimum amount of fuel will insure not only good fuel economy, but also reduce exhaust gas emissions. Thus, it is important to control the air/fuel ratio supplied to an engine as accurately as possible and this requires some method of accurately measuring the amount of air consumed by the engine.
It has been recognized that with two cycle, crankcase compression, internal combustion engines, pressure variations in the crankcase chamber can provide an accurate indication of the air being consumed by the engine. That is, by comparing the pressure in the crankcase chamber adjacent the times of opening and closing of the scavenge port, it is possible to determine the amount of air flowing to the cylinder in each cycle. Thus, such pressure sensing air measuring devices are extremely effective in providing good fuel economy and good exhaust emission control.
With a two cycle engine, however, there is fairly substantial overlap between the opening of the scavenging port and the closing of the exhaust port. Therefore, there exist a possibility that some of the burning charge from the cylinder can enter into the crankcase chamber and adversely effect not only the pressure reading of the pressure sensor but can actually damage the pressure sensor.
Where multiple cylinder engines are employed, it is generally the practice to only sense the pressure in one crankcase chamber in order to measure the air flow. This assumes that the air flow to all of the cylinders is either substantially equal or adjustments may be made in the amount of fuel supplied depending upon the physical orientations of the cylinders from known variations from cylinder to cylinder. Hence, if the single sensor that is used gives an erroneous reading, all cylinders will be affected.
It is, therefore, a principal object to this invention to provide an improved method and apparatus for sensing the air flow to an internal combustion engine for controlling its fuel supply.
It is a further object to this invention to provide an improved method and apparatus for crankcase pressure sensing and in which the device accommodates conditions when the pressure sensor may not give an accurate signal.
It is a further object to this invention to provide an improved method and apparatus for protecting the crankcase pressure sensor of a two stroke, crankcase compression internal combustion engine.
It is a further object to this invention to provide a method and apparatus for controlling the amount of fuel supplied to a two stroke, internal combustion engine through the sensing of the pressure in only one of multiple crankcase chambers and also which affords an alternate control routine under circumstances when the pressure signals may not be accurately indicative of actual air flow to the engine.